Prior art paper punches typically use a direct force approach to punch holes in a stack of paper sheets. In these prior punches, the user presses down on a pivoting cover flap which forces the punch pins down and into the paper stack. This direct force approach has very little mechanical advantage. The force required to punch through the holes increases with the thickness of the paper stack. For thicker paper stacks, the required force to punch through the stack may exceed what the user can easily provide.
To address this problem, several punch manufacturers have proposed using a lever mechanism to reduce the required force by increasing the mechanical advantage. For example, U.S. Pat. No. 5,778,750 proposes the use of an elongated lever handle where one end of the handle is pivotally fixed to the punch and the other end is pressed down by the user. In turn, an intermediate surface (between the ends of the handle) is forced down on the cover flap to exert the punching force. In U.S. Pat. No. 6,109,155, a lever handle is pivotally attached to a rod extending up from the based and through the cover flap. As in the '750 patent, when the handle is pressed down by the user, an intermediate surface on the lever presses down on the cover flap to exert the punching force. Both of these patents disclose the use of a lever handle to increase the force applied to the cover flap by mechanical advantage. This effectively reduces the maximum force the user needs to apply to punch the paper stack.
The present invention offers a novel lever-handled paper punch which increases the mechanical advantage in a different manner than other proposed lever punches. The present punch reduces the maximum punch force and improves upon the disadvantages of prior art punches.